The invention concerns a sample exchange device comprising a circumferential chain, sample receptacles which are disposed on the chain at equal distances and are connected to each other via webs, and a measuring and transfer position, wherein each sample receptacle can be transferred to the measuring and transfer position by moving the chain.
A sample exchange device of this type has been disclosed by the commercially available automatic sample exchanger “B-ACS60/120” by Bruker BioSpin GmbH, Rheinstetten, DE.
Spectroscopic methods are frequently used in instrumental analysis for examining the chemical composition of samples.
In NMR spectroscopy, for measuring a sample, the sample is e.g. moved to a strong static magnetic field and radio frequency (RF) pulses are irradiated into the sample. The reaction of the sample to the RF pulses is measured. The static magnetic field is generated by superconducting magnet coils. In modern NMR spectrometers, the magnet coils are cooled with liquid helium in a cryostat.
In order to maximize economical use of a spectrometer, the time required for changing between different samples should be minimized. In order to obtain a high sample throughput in spectrometers, automatic sample exchangers are normally used.
Automatic sample exchange in NMR spectrometers is realized by transferring a sample from a sample storage (containing a plurality of samples) to a measuring location in the room temperature bore (for example a vertical neck tube) of the cryostat and back.
The above-mentioned sample exchange device “B-ACS 60/120” by Bruker BioSpin GmbH for NMR spectrometers comprises an approximately ovally spanned, circumferential chain comprising a plurality of sample receptacles. The circumferential chain is spanned by two flatly oriented discs. Each sample receptacle may be provided with one sample (typically one glass capillary as a sample container including a substance to be measured inside the sample container, comprising a sample holder mounted to the sample container including a closing lid for the sample container). A transfer means may access a given sample when the associated sample receptacle is disposed at a certain transfer position, and move it to the neck tube of a cryostat. By moving the circumferential chain, each sample receptacle can be moved to the transfer position. This conventional sample exchange device is advantageous in view of the simple construction of the transfer means which requires only two directions of motion with stops and can be pneumatically operated. The circumferential chain can be driven using a simple construction, and also in a pneumatic fashion. This eliminates disturbance of the NMR measurement. The fact that the chain including sample receptacles require a great deal of space is, however, disadvantageous. Automatic devices for sample preparation additionally generally provide samples having rectangular sample grid in sample libraries, such that, in general, automatically prepared samples must be initially transferred to the circumferential chain.
There are further automatic sample exchangers of the type “SampleRail” for NMR spectrometers, disclosed by the company Bruker BioSpin GmbH, Rheinstetten, DE, which cooperate with an xyz robot arm that directly accesses samples from a sample library and moves them to the neck tube of a cryostat. Transfer of automatically prepared samples is thereby omitted, but the electromotive drive of the xyz robot arm could disturb the NMR measurement. With different motor settings, in particular, the magnetic stray field may vary, thereby falsifying the NMR measuring results.
It is the underlying purpose of the present invention to provide an automatic sample exchange device, in particular, for NMR spectrometers, which is particularly economical and does not impair the analysis of the samples.